12 hour internet outage every night between 7 and 9:30 PM

Every night between the hours of 7:00 PM and 9:30 PM the internet goes out and does not come back for 12 hours.  I have had multiple technician visits. They have changed the modem three times and replaced the line from the street to my house.  Every technician and agent I have spoken with promises that it has been fixed and every night it goes down. This has been going on for almost three weeks. When I speak to an agent, they indicate they only see outages in their system for a few minutes at a time. I even put in an escalation ticket and a regional manager was supposed to call. The next morning the escalation ticket was closed with zero explanation and no resolution. We are paying for a service that we are not receiving and we have had it